This invention pertains to the preparation of stable aqueous microemulsions of carboxylic acid or sulfonic acid containing vinyl resins in a solvent/cosolvent mixture by converting said vinyl resins to ionomers.
Vinyl resin lacquers are old in the art and have enjoyed commercial success for coating various substrates with clear vinyl coatings. The coating operation however, involves the removal of large quantities of organic solvents in which the vinyl resins are dissolved. For ecological and anti-pollution considerations solvent based coatings are undesirable. This has led to consideration of water-borne resin system for coating applications. It has not been found feasible to simply substitute a water-borne system for the vinyl resin lacquers for several reasons. While one may make vinyl resin latexes by emulsion polymerization these polymerization techniques require the presence of components in the polymerization recipe which have a deleterious effect on the final coating. This is particularly true in can coatings where such criteria as blush resistance and water resistance, particularly at pasteurization temperatures is required. The presence of surfactants required to maintain stable emulsions increases the susceptibility of resin coatings on substrates to break down in contact with water.
It is therefore an object of this invention to afford a water-borne vinyl resin which is free of surfactants.